The tripod mount, which is offered by GumpTrade, originates from the manufacturer JYC (Tripod Mount Ring A-2 for Canon Lens) and apparently has the same locking mechanism as the original Canon-clamp (a kind of snap, thanks to a spring-loaded pin snaps). By turning the set screw the lens is fixed, solves one the screw, you can rotate the camera and lens in the clamp, in order to take pictures with a constant focus in portrait mode. If you want to remove the clamp from the lens, you have to not only turn the screw, but pull "outwards". Inadvertent opening is thus prevented. Inside the collar lined with a velvet-like material, so that the lens is not scratched when turning. For safety's sake, I have a small, uneven place of aluminum clamps reworked with a file, so that nothing scrubs. In most "imitation" clamps the locking mechanism is different. There is rather a danger that gets a good piece scratches when releasing the clamp and turning the lens, because there are sharp edges on the closure. The painting corresponds to the lens. It is looked at closely, perhaps minimal dark, but that falls not on. So far I am satisfied, let's see how it is reflected in practice. By the way, the size of the lens, some might say that it takes no clamp. For handheld shots, I agree with this statement, but when using a tripod to prevent this (at least in the mounted battery grip) an annoying "sagging".
